Tonlé Sap Lake
Tonlé Sap Lake is the largest freshwater lake in Southeast Asia, located in central Cambodia. It plays a vital role in the country’s ecology, economy, and culture, serving as a key source of fish, irrigation water, and flood regulation. Its unique seasonal expansion makes it one of the world’s most productive inland fisheries.
Key facts
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Location: Central Cambodia
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Type: Freshwater lake and floodplain system
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Average area: 2,500 km² (dry season) to over 15,000 km² (wet season)
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Outflow: Tonlé Sap River → Mekong River
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UNESCO status: Tonlé Sap Biosphere Reserve (designated 1997)
Seasonal Hydrology
Tonlé Sap’s defining feature is its reversible flow. During the wet season (May–October), monsoon rains swell the Mekong River, reversing the flow of the Tonlé Sap River and expanding the lake up to six times its dry-season size. In the dry season, the flow reverses again, draining into the Mekong and shrinking the lake. This hydrological rhythm sustains rich wetlands and supports extensive fisheries.
Biodiversity and Ecology
The lake and its floodplain host diverse habitats—flooded forests, grasslands, and swamps—home to hundreds of fish species, migratory birds, and endangered animals such as the Siamese crocodile and Irrawaddy dolphin. Its ecosystem underpins the livelihoods of millions of Cambodians through fishing, agriculture, and ecotourism.
Human Settlements and Economy
Numerous floating and stilted villages, such as Kampong Phluk and Kampong Khleang, adapt to the lake’s seasonal rise and fall. The Tonlé Sap fishery provides up to 60% of Cambodia’s protein intake, making it a cornerstone of national food security and a cultural emblem.
Environmental Concerns
Tonlé Sap faces growing threats from upstream dams, overfishing, and climate change, which disrupt its natural flood pulse. Sediment loss and declining fish stocks pose risks to biodiversity and rural livelihoods. Regional conservation and management efforts aim to balance ecological protection with the needs of local communities.
